PDPs (plasma display panels) utilizing discharge phenomenon have been used as display panels for television sets, office automation apparatuses such as personal computers and word processors, traffic control signs, signboards, and other display boards.
The display mechanism of a PDP basically comprises two glass plates, a large number of discharge cells formed by partitions between the two grass plates, and fluorescent substrates within the respective discharge cells. The fluorescent substrates are selectively excited to emit light by discharge, thereby displaying characters and/or figures. An exemplary embodiment is shown in FIG. 16. In FIG. 16, reference numeral 21 designates a front glass, 22 designates a rear glass, 23 designates partitions, 24 designates display cells (discharge cells), 25 designates auxiliary cells, 26 designates cathodes, 27 designates display anodes, and 28 designates auxiliary anodes. Disposed in each display cell 24 is a red, green, or blue phosphor (not shown) which is a film-like form attached to the inside thereof. These fluorescent substrates emit light by electrical discharges when a voltage is applied between electrodes.
From the front surface of the PDP, electromagnetic waves with frequency from several kHz to several GHz are generated due to applying voltage, electrical discharge, and light emission. The electromagnetic waves are required to be shielded. In addition, for improving its display contrast, reflection of external light at the front surface is required to be prevented.
In order to shield such electromagnetic waves from PDP, conventionally, a transparent plate which has functions such as electromagnetic-wave shielding function is disposed in front of the PDP.
Electromagnetic-wave shielding material as mentioned above is also utilized as a window of a place where a precision apparatus is installed, such as a hospital or a laboratory, in order to protect the precision apparatus from electromagnetic waves for example from cellular phones.
A conventional electromagnetic-wave shielding and light transmitting plate typically comprises transparent substrates such as acrylic boards and a conductive mesh member like a wire netting or a transparent conductive film and is formed by interposing the conductive mesh member or the transparent conductive film between the transparent substrates and uniting them.
A conductive mesh member which is employed in the conventional electromagnetic-wave shielding and light transmitting plate is a 5- to 500-mesh member having a wire diameter from 10 to 500 μm and an open area ratio (open area percentage) less than 75%. The electromagnetic-wave shielding and light transmitting plate employing such a conductive mesh member has low light transmittance of 70% at the most.
Moreover, a display comprising an electromagnetic-wave shielding and light transmitting plate with such a conventional conductive mesh member easily allow the production of moire patterns due to relations between its patterns and pixel pitch.
As means for solving these problems, it has been proposed to use a pattern-etched conductive foil as an electromagnetic-wave shielding layer instead of the conductive mesh (JP 2000-174491A). An electromagnetic-wave shielding and light transmitting plate provided with the pattern-etched conductive foil having desired line width, distance, and mesh configuration has excellent electromagnetic-wave shielding characteristics and a high level of light transmittance and can prevent moire phenomenon.
The pattern etching of this conductive foil is achieved by bonding a metal foil onto a surface of a transparent substrate film, attaching a photoresist film to the metal foil with pressure, and etching into a predetermined pattern through pattern exposure and etching steps. Accordingly, the metal foil is provided as a film laminated on the substrate film.
An electromagnetic-wave shielding film comprising such a laminated film of the metal foil/the substrate film can not have sufficient visibility because light is reflected at the surface of the metal foil.